The present invention is related to load responsive brake apparatus and more particularly to a variable load valve device that provides brake pressure according to the effective pressure of air springs that support and thus reflect the load carried by the vehicle.
Typically, the load dependent air spring pressure acts on an actuating member in opposition to a helical control spring. The position of this actuating member conditions a relay valve to provide braking pressure according to the vehicle load. In order to adapt the variable load valve device to vehicles having different conditions of utilization, it is possible to not only adjust the spring tension, but also the spring deflection for a given load. The spring tension adjustment is normally carried out by means of an externally accessible adjusting screw, whereas the degree of spring deflection is controlled by adjusting the number of spring coils by rotation of a clamp device having a spiral groove about its periphery for engagement with the helical control spring. The spring tension adjustment is accomplished, as above mentioned, by an externally accessible adjusting screw and thus requires no disassembly or replacement of the components. Adjustment of the clamp device to vary the number of active spring coils, however, does require disassembly of the adjusting components including the spring tension adjustment screw.